Telecommunications networks and systems, including wireless networks and systems, use signaling provided over a signaling network to set up and tear down calls and to perform non call-setup or transaction functions such as the various services offered by an Advanced Intelligent Network (AIN) . Generally, signaling functions may be grouped into call-setup functions and non call-setup or transaction functions. The call-setup functions are concerned with setting up and then releasing or tearing down calls, while the non call-setup or transaction functions involve providing services that generally require a database query to determine how to proceed with a call. A few examples of the non call-setup or transaction functions include toll-free number routing, credit card validation and roaming in wireless telecommunications networks.
Today, digital signaling networks use a newer out-of-band signaling system and protocol developed by the International Telegraph and Telephone Consultative Committee (CCITT) and called Signaling System 7 (SS7). SS7 provides a layered functional structure and uses destination routing, octet oriented fields, variable length messages, and a highly reliable message transfer protocol. SS7 also provides flow control, connection and connection-less services, and Integrated Services Digital Network (ISDN) capabilities. Out-of-band signaling and SS7 solve many of the disadvantages associated with older in-band signaling techniques. A signaling network implementing SS7 may be referred to as an SS7 signaling network.
A typical SS7 signaling network will include a local digital switch, which may be referred to as a Service or Signal Switching Point (SSP), transmission facilities with associated transport devices including a first channel bank and a second channel bank, a Signal Transfer Point (STP), and a Service Control Point (SCP) . The STP may be implemented as a specialized packet switch optimized for SS7 packets. The SCP may be used to control an associated local digital switch, or a tandem switch in other embodiments, that supports AIN services (also referred to as AIN applications), and may be implemented as a computer and associated database that includes network and customer-specific information to perform such tasks as call routing and number (address) translation to deliver network services.
SS7 uses a Point Code (PC) to identify each node of a telecommunications network and a Sub-System Number (SSN) to identify particular elements or sub-systems of each node. A PC is unique for each node of a particular telecommunications network, but it is not unique across multiple networks. As a result, a PC and an SSN cannot be used to uniquely identify a particular node or a particular sub-system of a network for inter-network communications. Instead, SS7 uses a Global Title (GT) to uniquely identify each node and sub-element of every telecommunications network. A GT, unlike a PC, is unique for every node of every network; thus, a GT may be used for inter-network communications to uniquely identify every node and every sub-system of every telecommunications network. The GT may undergo one or more Global Title Translations (GTTs) before for example, a message is delivered to a destination node and sub-system. As a result of the one or more GTTs, the PC and SSN of a particular local element or sub-system is ultimately revealed.
The SS7 protocol includes a layered functional structure that is comprised of various layers or parts.
Generally, originating messages, including destination addresses, are provided from upper layers or parts to lower layer or parts. The various layers or parts concerned with the non call-setup or transaction functions are outlined below. Generally, the non call-setup or transaction functions include both transport functions and transaction functions.
The transport functions are divided into four parts that include a Message Transfer Part (MTP) that comprises three of the four parts and a Signaling Connection Control Part (SCCP) that comprises the fourth part. These four parts of the transport functions may be designated as the MTP 1, the MTP 2, the MTP 3 and the SCCP and are listed from lower to higher layers or parts. The three MTP parts provide functions for basic routing of signaling messages between signaling points. The MTP parts preferably use PCs provided in a MTP message to provide the basic routing of signaling messages between signaling points. The three MTP parts also provide the complete lower level functionality at the Physical, Data Link and Network Level. The SCCP part resides above the three MTP parts and provides additional routing and management functions to the MTP for the transfer of messages other than call setup between signaling points. The SCCP may include a routing table and supports higher level layers, detailed below, with an array of services including both connection-less and connection oriented services. The SCCP can perform GTTs to generate a PC and SSN that are used to convert an SCCP message to an MTP message by adding an MTP header to an SCCP message.
The transaction functions of the SS7 protocol include a Transaction Capabilities Application Part (TCAP) and an application or user part (hereinafter application part). The TCAP resides above the SCCP and provides for the exchange of non-circuit related, transaction-based information between signaling points and network entities that include signaling functions for communication with network databases. The TCAP includes building blocks that may be subdivided into the transaction sublayer and the component sublayer. The TCAP can generate an SCCP message by adding an SCCP header to a TCAP message. The Application Part may be defined as an application which resides above the TCAP and which may generate a TCAP message or primitive for use by the TCAP. For example, the following applications or services may be referred to as an application part: the Mobile Application Part (MAP), including at least an Interim Standard 41 (IS-41) and a Global System for Mobile Communications (GSM) standards that address registration of roamers and intersystem hand-off procedures, an Interim Standard 634 (IS-634), an Intelligent Network Application Part (INAP), an Intelligent Network Capability Set (INCS) application, an AIN application and any other application which uses the TCAP. The application parts may use an application provider and the like to generate a TCAP message from an application part message for use by the TCAP.
An example of the operation of an application provider of an application part may be illustrated by the operation of a MAP Provider of a GSM MAP. The MAP represents a set of procedures that provide the bridge between the various sub-systems of a GSM wireless telecommunications system to support subscriber unit mobility. Such sub-systems may include a Mobile Switching Center (MSC), a Visitor Location Register (VLR), and a Home Location Register (HLR). The MAP support includes management of subscriber location, transfer of subscriber data between network elements, call set-up and subscriber database fault recovery. The MAP Provider furnishes the interface for MAP dialogues between, for example, the MSC, VLR, and HLR.
For example, assume that a common node, such as a wireless telecommunications system, has a first sub-system, such as a VLR, and a second sub-system, such as an HLR, and the first sub-system desires to send a MAP message to the second sub-system. The MAP Provider receives the MAP message provided by the first sub-system and generates a TCAP message in response. The MAP Provider may attach a TCAP header to the MAP message to generate the TCAP message, such as by converting a MAP primitive to a TCAP primitive. TCAP then receives the TCAP message and converts it to an SCCP message by attaching or including an SCCP header. An SCCP then receives the SCCP message and performs a Global Title Translation (GTT) to determine the destination address of the message. When it is discovered that the message is destined for the second sub-system of the common node, the SCCP message is then sent back to the TCAP. The TCAP generates a TCAP message by removing the SCCP header. The MAP Provider in turn receives the TCAP message and generates the original MAP message by removing the TCAP header. The MAP message is then sent to the second sub-system of the common node.
Thus, whenever a MAP message is destined for a local sub-system or sub-element, significant processing capability is consumed only to determine that the MAP message should be provided back to a local sub-system. The MAP Provider example illustrates that five conversions are performed on the MAP message after it is received by the MAP Provider only to determine that the MAP message was destined for the second sub-system of the common node. These additional conversions consume considerable processing resources and harm overall performance of a telecommunications system and signaling network. Further, these additional conversions unnecessarily consume the limited resources of the MAP Provider and the TCAP. Specifically, these additional conversions unnecessarily consume resources used to process dialogues. As a consequence, the overall bandwidth of the wireless telecommunications system may be reduced, fewer subscribers may be supported and telecommunications services, such as AIN and roaming, may not be as timely provided.
Application providers, other than MAP Providers, also suffer from this significant disadvantage such that signaling communication between local sub-systems of a common node, which are frequently needed, require multiple transactions using various SS7 layers or parts as illustrated above in the MAP Provider example. This is inefficient and further increases congestion and loading of the SS7 signaling network.